In direct contact steam injection heaters, steam is directly mixed into a flowing fluid (e.g. liquid or slurry) to heat the flowing fluid. Direct contact steam injection heaters are well known in the art and are very effective at transferring heat energy to the flowing fluid. They provide rapid heat transfer with virtually no heat loss to the atmosphere, and also transfer both the latent and the available sensible heat of the steam to the liquid or slurry.
A shortcoming of existing injection heater designs is that they are only operable at relatively low steam pressures. While adequate for most applications, existing diffuser style injection heater designs are unable to handle steam pressure in excess of approximately 300 psi. Generally speaking, power plants and other facilities with boiler operations have steam pressure in the 250-1200 psi range.
Previous designs of diffuser-type steam injection heaters employ elastomeric, or otherwise pliant, seal elements between the regulating member and the diffuser. In such configurations, a lower seal is intended to prevent steam from leaking around the distal end of the regulating member and into the fluid chamber. An upper seal is intended to prevent steam from leaking between the diffuser and the regulating member.
In the experience of this inventor, such seals can quickly wear out as they ride over the diffuser when the regulating member moves. Moreover, such pliant seals, which may be acceptable at lower pressures, are completely unsuitable for use at higher steam pressures. As a result, in prior heaters, it is difficult to prevent the flow of steam into the diffuser when, for example, it is desired to stop the flow of steam into the fluid to be heated. Therefore, what is needed is a new seal configuration to prevent steam from leaking past the upper seal so that steam can only enter the fluid to be heated through the regulating member.